Fearful experiences passed on in mice families, study finds

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A newborn mouse pup, seemingly innocent to the workings of the world, may harbor generations' worth of information passed down by its ancestors.

Researchers taught male mice to fear the smell of cherry blossoms by associating the scent with mild foot shocks. Two weeks later, they bred with females. The resulting pups were raised to adulthood having never been exposed to the smell.

Yet when the critters caught a whiff of it for the first time, they suddenly became anxious and fearful. They were even born with more cherry blossom-detecting neurons in their noses and more brain space devoted to cherry blossom-smelling.

The memory transmission extended out another generation when these male mice bred, and similar results were found.

Neuroscientists at Emory University found that genetic markers, thought to be wiped clean before birth, were used to transmit a traumatic experience across generations, leaving behind traces in the behavior and anatomy of pups.

The study, published online on Sunday in the journal Nature Neuroscience, adds to a growing pile of evidence suggesting that characteristics outside of the strict genetic code may be acquired from our parents through epigenetic inheritance. Epigenetics studies how molecules act as DNA markers that influence how the genome is read. We pick up epigenetic markers during our lives and in various locations on our body as we develop.

Through a process dubbed “reprogramming,” these epigenetic markers were thought to be erased in the earliest stages of development in mammals. But recent research — this study included — has shown that some of these markers may survive to the next generation.

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